lotterydrawing.java

模拟抽彩游戏,调用Java.util.Arrays类中的 sort方法

/**
   @version 1.10 1999-12-17
   @author Cay Horstmann
*/

import java.util.*;
import javax.swing.*;

public class LotteryDrawing
{  
   public static void main(String[] args)
   {  
      String input = JOptionPane.showInputDialog
         ("How many numbers do you need to draw?");
      int k = Integer.parseInt(input);

      input = JOptionPane.showInputDialog
         ("What is the highest number you can draw?");
      int n = Integer.parseInt(input);

      // fill an array with numbers 1 2 3 . . . n
      int[] numbers = new int[n];
      for (int i = 0; i < numbers.length; i++)
         numbers[i] = i + 1;

      // draw k numbers and put them into a second array

      int[] result = new int[k];
      for (int i = 0; i < result.length; i++)
      {  
         // make a random index between 0 and n - 1
         int r = (int)(Math.random() * n);

         // pick the element at the random location
         result[i] = numbers[r];

         // move the last element into the random location
         numbers[r] = numbers[n - 1];
         n--;
      }

      // print the sorted array

      Arrays.sort(result);
      System.out.println
         ("Bet the following combination. It'll make you rich!");
      for (int i = 0; i < result.length; i++)
         System.out.println(result[i]);

      System.exit(0);
   }
}